let's bring in the head of the department of medicine at vanderbilt university medical center in nashville. great to see you again. >> hello, shepherd. >> sarin, tell us about it. what does it do? >> it is nasty and sneaky. it is odorless, tasteless and colorless. it is produced in a liquid form and vaporizes very quickly. you can get exposed by breathing it in. if can come in through your eyes. it can penetrate your skin. if it is on food or water you can ingest it. it obviously causes eye irritation, but most importantly it causes great difficulty breathing because it is a neurological toxin. it makes your muscles twitch. you can develop convulsions and lapse into coma and die. it is serious stuff. >> and it is my understanding, doctor, if you are not treated almost immediately like within a minute or so, there is no stoping the affects. >> well, mild exposures just wafting through the air can lead to being temporarily ill and then getting better. if you get a prolonged dose you can get really sick very, very quickly. furthermore it can get on your clothes and then it can vaporize from t